Berlin 2008 – scientific programme

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MA: Fachverband Magnetismus

MA 11: Spindependent Transportphenomena II

MA 11.5: Talk

Monday, February 25, 2008, 16:15–16:30, H 0112

Effects of Ga⁺ irradiation on the magnetotransport in NiFe — •André Kobs, Daniel Stickler, Matthias Scholz, Germar Hoffmann, and Hans Peter Oepen — Institut für Angewandte Physik, Universität Hamburg, Jungiusstr. 11, 20355 Hamburg, Germany

The influence of irradiation by 30 keV Ga⁺ on Pt capped NiFe wires were studied and quantified with in situ magnetotransport measurements. The wires were milled from 33 nm thick film and then irradiated with 30 keV Ga⁺ varying the dose from 5· 10¹⁴ to 1· 10¹⁷ Ions/cm² using focused ion beam (FIB). The magnetoresistance (MR) behaviour of the structures was determined in current-longitudinal-to- and current-transversal-to-applied-field-geometry via in situ measurements utilizing a micromanipulator. The NiFe wires exhibit the typical anisotropic MR. In the transversal setup an enhancement of ΔR up to doses of 8· 10¹⁵ Ions/cm² in comparison to the untreated NiFe was observed. For higher doses an exponential decrease of ΔR with dose occurred. The increase of the resistance on ion bombardment can be explained with impurity scattering caused by gallium implantation and intermixing of Pt and NiFe, roughening of surface and material removal. The rate of material removal and the root-mean-square roughness have been determined by means of atomic force microscopy (AFM). The changes of composition were monitored by energy-dispersive x-ray spectroscopy (EDX). The magnetic properties were investigated by longitudinal magneto-optical Kerr effect (MOKE). The results of the latter investigation demonstrate the correspondence of features in the magnetisation and MR behaviour.